Little is known about the causes of lung cancer in nonsmokers. The objective of this proposal is to identify risk factors for lung cancer in nonsmokers using existing data collected in a multicentered study of lung cancer in nonsmokers. The primary goal of this multicentered study was to determine if passive smoking causes lung cancer in nonsmokers. We now would like to use the data collected in this study to evaluate: a) the role of indoor air pollution from a variety of sources as a cause of lung cancer; b) the relationship between intake of vegetables, fruits, and carotenoids and risk of lung cancer; c) the relationship between previous lung diseases and risk of lung cancer; d) The relationship between family history of cancer and risk of lung cancer; and e) The role of occupational exposures as a risk factor of lung cancer. Data are available on about 650 lung cancer cases, 1200 population-based controls, and 350 colon cancer controls who were interviewed in 5 metropolitan areas in the US (Atlanta, Houston, Los Angeles County, Louisiana, and San Francisco Bay Area) between 1985 and 1991. The independent effect associated with each of the above factors and its potential confounding effect on the passive smoking-lung cancer association will be evaluated. Data analyses will include examining each of the suspected risk factor stratified by relevant covariates (e.g. race, age, study area). Odds ratios and corresponding confidence intervals will be calculated to estimate the lung cancer risk associated with exposure to each of the suspected factors. Multiple logistic regression models will be used to determine whether any of the observed risk factors are confounders for other risk-factors relationships.